The impact of energy density and process parameters on the distribution of residual stresses in additively manufactured stainless steel 316 L

The current investigation involves the fabrication of fifteen samples of austenitic stainless steel 316 L (SS316L) utilizing laser powder bed fusion technology to evaluate the residual stresses through the impact of energy density, which was varied between 30 J/mm³ and 111 J/mm³ by varying process parameters, notably scanning speed and laser power. The energy density range suggested by existing literature has been found to have samples with significant mechanical properties, apart from its impact on residual stress, which can affect the service life of the product. The primary focus of this study is to identify the optimal window for achieving residual stress at various locations within the sample. The study discovered differences in residual stress development at all tested locations. When employing lower laser powers of 140 W and 160 W, residual stress formation remained consistent. Furthermore, when the laser power exceeds 140 W to 160 W, a substantial temperature gradient develops, leading to a considerable rise in tensile stress magnitude. The variation in energy density does not affect residual stress, while there is a variation in two process parameters, laser power and scanning speed, simultaneously. A laser power range of 140 W to 160 W, combined with scanning rates ranging from 500 mm/s to 1100 mm/s, results in a consistent range of minimal residual stress formation across multiple locations. The key outcomes of the study show the crucial role of laser power and scanning speed in residual stress development, which has implications for improving mechanical characteristics and product service life by generating minimal residual stresses.